title: Import-defective colicin B derivatives mutated in the TonB box.
abstract: The pore-forming colicin B is taken up into Escherichia coli by a receptor and TonB-dependent process. The receptor and colicin B both contain a similar amino acid sequence, close to the N-terminal end, termed the TonB box. Point mutations were introduced into the TonB-box region of the colicin B structural gene cba resulting in colicin B derivatives which were partially or totally inactive against E. coli cells. All derivatives still bound to the receptor. An inactive derivative killed cells when translocated across the outer membrane by osmotic shock treatment, and formed pores in planar lipid bilayer membranes identical to the wild-type colicin. Some of the mutations were partially suppressed by mutations in the tonB structural gene. It was concluded that the TonB-box mutations define a region that is involved in the uptake of colicin B across the outer membrane.
authors.affiliation: Mikrobiologie II, Universität Tübingen, FRG.
authors.forename: J
authors.initials: J
authors.lastname: Mende
authors.forename: V
authors.initials: V
authors.lastname: Braun
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D003087:Colicins / Q000378:metabolism*; D004553:Electric Conductivity; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D008051:Lipid Bilayers / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009997:Osmotic Pressure; D015183:Restriction Mapping
chemical_list: D001426:Bacterial Proteins; D003087:Colicins; D029968:Escherichia coli Proteins; D008051:Lipid Bilayers; D008565:Membrane Proteins; C057616:tonB protein, Bacteria; C489181:tonB protein, E coli